Conventional projectors such as over head projector, slide projector, CRT (cathode-ray tube) projector, LCD (liquid crystal display) panel, DLP (digital light processing) projector, and so on are used to project text and/or images on a display area or panel for allowing more people to simultaneously view the text and/or images. An advanced projector can be connected to a notebook computer or a desktop computer, allowing data processed from the computer to be projected by the projectors without having to print out data on papers and thus free of concern that data may be unclearly shown on the papers and degrade quality of projection.
The foregoing projector can further be connected to a digitizing tablet which is a digital input board with a touch-sensitive surface on which a user may write with a touch pen. Moreover, the digitizing tablet can be connected to a computer by which text written on the digitizing tablet is converted via recognition software into readable data for the computer or user, or printed out by a printer connected to the computer. This also allows the projector to project an image displayed on a screen of the computer onto the digitizing tablet, whereby the user can use the touch pen as a pointing device to operate application programs executed by the computer.
FIG. 1 illustrates a connection structure of a digitizing tablet and a computer, which includes a digitizing tablet 10, a computer 20, and a projector 30.
The digitizing tablet 10 allows a user to write thereon with a touch pen 12 and accordingly generates associated pixel coordinate data to be sent to the computer 20 via a connection interface 11 such as a wired RS-232 interface or a wireless IrDA (infrared data association) interface. The computer 20 converts the pixel coordinate data into data readable for the computer or user, or prints out data via a printer (not shown) connected thereto.
The computer 207 such as a desktop computer or a notebook computer, is connected to the digitizing tablet 10 via the connection interface 11, for receiving and converting the pixel coordinate data from the digitizing tablet 10 into associated images or operating commands.
The projector 30 converts an image displayed by the computer 20 into an optical image and projects the optical image on the digitizing tablet 10. Thereby, the user may use the touch pen 12 as a pointing pen to select various operational functions displayed on the digitizing tablet 10.
However, in practice, the connection structure of the projector, digitizing tablet and computer renders the following disadvantages. It requires external cables for connecting the computer 20 and projector 30, besides, if the connection interface 11 is a wired RS-232 interface, more cables are used to connect the computer 20 and digitizing tablet 10. The use of cables undesirably makes the connection structure relatively messy in appearance. Furthermore, the user needs to adjust a projection angle of the projector 30 to align the projected image onto a projection screen for each time of operation, making the projection operation fairly time-ineffective to implement. In addition, movement of the user e.g. a speaker may easily interfere with the projected image on the projection screen, which would adversely affect attention of the audience or viewers and degrade quality of the image display.